Smart Manufacturing Connectivity for Brown-field Sensors Testbed – Initial Deployment – Report after Completion of Phase I An Industrial Internet Consortium Results White Paper IIC:WHT:IN27:V1.0:PB:20181023 Dr. Michael Hilgner (TE Connectivity) Erich Karl Clauer (SAP)
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Smart Manufacturing Connectivity
for Brown-field Sensors Testbed –
Initial Deployment –
Report after Completion of Phase I An Industrial Internet Consortium Results White Paper
IIC:WHT:IN27:V1.0:PB:20181023
Dr. Michael Hilgner (TE Connectivity)
Erich Karl Clauer (SAP)
Smart Manufacturing Connectivity for Brown-field Sensors Testbed – Completion of Phase I
IIC:WHT:IN27:V1.0:PB:20181023 - 2 -
This white paper provides an overview of the accomplishments of phase I of the “Smart Manu-
facturing Connectivity for Brown-field Sensors Testbed.” The testbed addresses the discrete
manufacturing domain where Programmable Logic Controllers (PLCs) typically govern local
control loops of sensors and actuators that are either directly connected to a PLC or via an
Input/Output module, an I/O module. The testbed focuses on a brown-field scenario where IO-
Link sensors are connected to an elderly PLC through an IO-Link master gateway, which is a
special active I/O module capable of mastering IO-Link devices. IO-Link is a digital interface that
enables a bidirectional data exchange with sensors and actuators.
The testbed comprises the development of a retrofittable hardware that is intended to replace
an existing I/O module and establishes a communication channel towards higher-level IT
systems, in addition to the channel used for the data exchange with the PLC. As this hardware
delivers data from a common source, namely a set of sensors, to two recipients, the higher-
level IT system and the PLC, it is called the “Y-Gateway.” The data exchanged through the two
communication paths are however quite different: The PLC is only provided with the data
required to run the original control task, whereas more comprehensive information is delivered
through the additional path to enable added value services. So, the (elderly) PLC is not
burdened with data processing beyond carrying out the functions for which it was once
selected and programmed.
The testbed further encompasses the definition and implementation of a consistent mapping
from IO-Link to OPC Unified Architecture (OPC UA). The result is an OPC UA device model with
standardized semantics that is used by the server-client-based data exchange between the Y-
Gateway and the IT system to facilitate the easy integration of the sensor data within the IT
system’s data base. Using OPC UA over TCP/IP for the additional channel established by the Y-
Gateway not only guarantees the semantic interoperability but also assures a secure
connection through OPC UA’s proven security mechanisms.
The testbed finally includes the implementation of a usage scenario that increases the overall
equipment effectiveness of a manufacturing process step by collecting data on consumed
resources by a set of IO-Link sensors and providing those to SAP Manufacturing Integration &
Intelligence (SAP MII) or SAP Cloud via the additional communication path that allows for the
implementation of added value service at the enterprise level.
The white paper describes the proposed solutions’ elements and fundamental capabilities and
the technical details have been made available to the Industrial Internet Consortium (IIC)
community via more comprehensive deliverables, such as a high-level description of the IO-
Link/OPC UA mapping, a report on the Y-Gateway’s endpoint security threat analysis, a
specification to measure the latency of the real-time path through the Y-Gateway, a description
of OPC UA’s communication security mechanisms and a report on the impact of applying
Smart Manufacturing Connectivity for Brown-field Sensors Testbed – Completion of Phase I
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This set of deliverables, including this white paper, documents the technical feasibility of the
testbed’s approach and shows the benefits for manufacturing operators, namely that
retrofitting a brown-field facility with just a few sensors and connecting them to the
appropriate platform solution provides quick insights into potential improvements and
optimization requirements.
INTRODUCTION INTO THE TESTBED
The Smart Manufacturing Connectivity for Brown-field Sensors Testbed is a joint effort of IIC
members TE Connectivity, a world leader in connectivity and sensors, and SAP, a world leader in
enterprise applications in terms of software and software-related service revenue. Additional
collaboration partners are ifm, a worldwide leader in sensors, controllers and systems for
automation and the OPC Foundation, the organization defining the industrial interoperability
standard OPC UA. The IIC Steering Committee approved the testbed in April 2016. Public
information is available on a dedicated web page under www.iiconsortium.org.
This testbed addresses the discrete manufacturing domain, traditionally characterized by a
strict hierarchical structure, referred to as the “Automation Pyramid.” At the control level of the
pyramid, PLCs manage the real-time sub-systems, including sensors and actuators, and provide
the connection to the enterprise IT systems. In this structure, any data generated by a sensor
passes through the PLC. Whereas planning a green-field installation generally considers the
capability of processing a high volume of data required by advanced (cloud-based) analytics for
the selection of the PLCs, in brown-field facilities, the PLCs are often capable of running the
automation sequence only.
Smart Manufacturing Connectivity for Brown-field Sensors Testbed – Completion of Phase I
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Figure 1: Traditional Automation Pyramid and additional communication path (“IoT data flow”) as
proposed by the testbed
The testbed extracts data from the real-time control system and delivers it to the higher-level IT
systems via an additional communication path without affecting real-time operations. This
solution comprises the following elements:
Retrofittable hardware, the “Y-Gateway,” with IO-Link, Industrial Ethernet and OPC UA
(TCP/IP) interfaces, that re-uses existing cabling.
The definition and standardization of a common device model to allow for the easy
integration with the IT system. This device model is based on the consistent mapping of
IO-Link parameters to OPC UA.
An IT platform that maintains the individual devices’ configurations and aggregates
process data to enable the implementation of applications.
The following sections provide more details on these elements and an example of how the
solution can be used to monitor the resource efficiency of a manufacturing process.
Y-GATEWAY
The Y-Gateway replaces a common I/O module. It has an interface to exchange data with the
connected IO-Link devices via OPC UA over TCP/IP, in addition to the interface to the industrial
communication system, e.g., an Industrial Ethernet such as PROFINET, Ethernet/IP or EtherCAT.
That data is extracted from a memory block used by the IO-Link master implementation and
Smart Manufacturing Connectivity for Brown-field Sensors Testbed – Completion of Phase I
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converted to OPC UA semantics in a separate processing unit on the Y-Gateway. This ensures
that real-time operations are not significantly delayed, as proven by dedicated latency
measurements. Figure 2 provides an overview of contributions to the overall system latency Tt
along the real-time path which is given by the sum Tt = TS1 + TS2 + TS3 where:
TS1 is the duration from an event at the input of the sensor to the transmission of the
respective message over the IO-Link channel,
TS2 is the latency in the I/O module or Y-Gateway, respectively, due to required
conversion steps between the IO-Link master input and the Industrial Ethernet output
and
TS3 is the conversion time from the PLC’s input to its digital output.
TS2 can be further broken down into
time intervals used by the IO-Link master stack for sampling (TIS) and processing (TIP),
the time TC taken by the required conversions and
the processing time TIE taken by the Industrial Ethernet software stack.
Figure 2: Contributions to the overall system latency of the real-time path
TC is the interval of interest here. In the case of the original I/O module, TC refers to the conversion to the Industrial Ethernet frames only, whereas for the Y-Gateway, TC is dominated by the time required for the IO-Link/OPC UA conversion. With the assumptions of TS3 << TS1 and TS3 << TS2 and measurements for reduced setups, TC can be determined for both cases. A measurement specification made available to the IIC members provides further details here.
The Y-Gateway can connect up to eight IO-Link sensors or actuators. It is delivered with a
configuration tool that provides an overview on the connected devices and enables the
association of process data with custom variables. The Y-Gateway also enables data preparation
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and combination of data from several IO-Link sensors prior to the delivery to the connected IT
system.
IO-LINK
The IO-Link technology provides a serial, bi-directional, point-to-point interface for the
connection of sensors and actuators to a control system, including a 24V power supply. There is
a set of IO-Link specifications published by the IO-Link Community. The fundamental IO-Link
specification is adopted as International Standard IEC 61131-9 (Programmable controllers—Part
9: Single-drop digital communication interface for small sensors and actuators (SDCI)) and
hence allows consistent integration with common industrial communication and automation
systems.
IO-Link is developed and promoted by the IO-Link Community (www.io-link.com). Testbed
partners TE Connectivity and ifm are members of that community. The IO-Link System
Description made available on www.io-link.com/en/Download/Download provides an overview
of the technology. An IO-Link system consists of the following basic components:
IO-Link devices (e.g., sensors, RFID readers, valves, motor starters and IO modules),
an IO-Link master that establishes the connection between the IO-Link devices and the
automation system, where one IO-Link device is connected to one port of the master
(point-to-point) and
unshielded (3- or 5-conductor) cables of up to 20 m to connect the devices and the
master.
According to the IO-Link Specification v1.1, IO-Link supports the modes with transmission rates
of 230.4, 38.4 and 4.8 kbaud. The response time of the system depends on the cycle times of
the devices. The minimum cycle time is specified for each device in the respective device
description (the IO Device Description or IODD).
Four types of data are communicated via an IO-Link Interface:
(cyclic) process data with a maximum of 32 bytes,
(cyclic) status data indicating the integrity of the process data (mostly transmitted
together with the process data),
(acyclic) device data providing parameters, identification or diagnostic information on a
device at the request of the IO-Link master and
(acyclic) events, such as error messages and maintenance warnings (e.g., in case of